SAP Message 6D721 - Due date &1 is not within interval &2 to &3

Diagnosis
The date you have entered does not lie within the first postingcycle (FrM field) of the condition type.

System Response
The system does not accept this date.

Procedure
Specify a date within the first posting cycle (FrM field) of thecondition type.
Example:
- Validity of condition: from 01/01/1999
- Posting cycle: 3 months
Therefore the date must lie between 01/01/99 and 31/03/99.